Author
Topic: Motorbike Lift Bench (Read 7878 times)

A "serious" project from me for a change, rather than the usual stuff 'n nonsense.

I've always done my own maintenance and servicing on my motorbike. However, as time goes by my knees and back seem to get less and less keen on the idea.So one of those nifty hydraulic bike benches began to look quite attractive. Thought about buying one, of course, but decided that would be just plain silly. Like you do...

No, it's obviously time to kick through the scrap pile and fire up the welder.

Base frame. A straightforward enough bit of fabrication. Some of this steel has been stored outdoors. Grind the rust off the areas to be welded. I'll deal with the rest later.

Parallel motion arms. Not working to a drawing, or even a rough sketch. Got picture in my head of how it will work, but basically making it up as I go along.

Pivot detail. Reinforced with 16 x 2 hydraulic tube, welded in place. Gives a nice fit on the M12 pivot bolts. The base is 50 x 50 box section, the arms are 40 x 40. So the tube projects 5mm either side to take up the play.

Clamps. The metal-bodgers best friend. Not even thinking about welding moving parts up at this stage. Too much head-scratching and pondering to do. Arms swing quite nicely, though...

I bought a bike lift when i retired from work for the same reasons, to many years on my knees.i have just fitted a new clutch to the Lads GSF600, i have an old Douglas Vespa on it at the momentbringing it back to life for a mate, it was his Dads ( 1959 ) 150ls2.. What i was getting at is....I think in the 8years i have had the lift i have only ever raised it half a dozen times i'm sure I still go down on my knees so whats that all about!!!

When not in use mine is stored standing upright against the shop wall.

A few mates have built their own & there are plenty of free plans & build logs to guide you. One thing that I consider essential with these is a means of locking the table rigid. When your pride & joy is up there it can make you very nervous when it starts rocking back & forth every time you lay on the hands !

My ultimate self build would be flush with the shop floor & either air or electric push button lift.

Plan A was to use a trolley jack, as I thought that would keep things simple.However, because the lift arm on the jack and the PM arms on the bench are different lengths, making it work properly leaves you with a couple of design choices.

First is to allow the jack to do what trolley jacks do, roll backwards and forwards as it raises and lowers, to compensate for the different radii of motion. This means having a solid base or some kind of trackway in the base frame, capable of taking the full load. It also seemed to mean that the fully-lowered height was more than I was happy with.

The other choice was to remove the wheels and weld the jack chassis into the base frame, with the lift arm pivot exactly concentric with one of the PM pivots. All good unless the jack ever failed and needed fixing. The only way would be to cut the whole thing apart.

I guess neither problem would be insurmountable, with enough ingenuity. But it still seemed to be making things more complicated, not less. Besides, by then I'd found this on Ebay.

8 tonne lift capacity and an impressive ram extension. Seems as though it might simplify things considerably. Still left me with one really puzzling question, though.How do the Chinese manage to make this thing, ship it half way around the planet, and drop it on my doorstep, all for £24.99?

Bottom ram pivot. This will get some bracing around it before we're done.

This is where it will live...probably.

Top ram pivot. Tacked into place, ready for a quick test.[/url]

First try. Quick pump up. With the ram at full extension, the PM arms will still be on the safe side of vertical.Saves me having to build some kind of dead-stop in. In this position the table height will be approx. 760mm . About right, then.

Tried the other PM arm, but because of the revised design it's cross brace fouls the ram body. There may be a way round it, if not I'll cut it out and carry on.

Looking at the design of the piston anchor on your frame and wondering if it would be better welded on the inner surface of the cross member so that the strain is taken by the cross member and the side plates instead of the just the welding of the side plates. Just a thought!

Looking at the design of the piston anchor on your frame and wondering if it would be better welded on the inner surface of the cross member so that the strain is taken by the cross member and the side plates instead of the just the welding of the side plates. Just a thought!

If I'm understanding you question correctly, then it works like this. (I think )

In the fully-down position, the ram body pivot, the piston pivot and the bottom pivot of the arm would be almost in a straight line. So when you started to lift, a large proportion of the ram force would go into simply trying to bend the cross member instead of lifting the load.

By offsetting the top pivot in that way it "breaks the angle" and turns the pushing force from the ram into a turning moment around the arm's bottom pivot. The alternative would be to stop the table going low enough to line up the three points, which makes it a little more difficult to get a heavy bike on board.

You're right in what you are saying, about it being less than ideal from a structural point of view at that point, but it was a compromise I'm willing to make to get the loading height as low as possible.

If I'm understanding you question correctly, then it works like this. (I think )

In the fully-down position, the ram body pivot, the piston pivot and the bottom pivot of the arm would be almost in a straight line. So when you started to lift, a large proportion of the ram force would go into simply trying to bend the cross member instead of lifting the load.

By offsetting the top pivot in that way it "breaks the angle" and turns the pushing force from the ram into a turning moment around the arm's bottom pivot. The alternative would be to stop the table going low enough to line up the three points, which makes it a little more difficult to get a heavy bike on board.

You're right in what you are saying, about it being less than ideal from a structural point of view at that point, but it was a compromise I'm willing to make to get the loading height as low as possible.

I think that while the lift may work as it is, it will struggle or fail when a bikes weight is on itAdding a set of maybe 2in. pieces between top and bottom platforms would helpThe working angle of the ram means that lift per pump stroke is at its maximum when the lift is in the down positionWith a a ramp on the end of the lift a couple of more inches will not hurt too muchIt would be wise to also fit a mechanical lock to prevent the lift platform resting on the hydraulic ram when in the raised positionI made my own "scissors" type lift and used a trolley jack to operate it, I keep meaning to go and redesign the lifting mechanism and use something like an acme screw ???My second bike bench is made from an old hospital bed , hydraulics already in place

JohnHa, Very appropriate "My second bike bench is made from an old hospital bed , hydraulics already in place". After all, these lifts are for "sick" bikes are they not? At least one needing some (medical) intervention.John B

Logged

Converting good metal into swarf sometimes ending up with something useful. ;-)

OK, so this project has progressed somewhat more rapidly than my updates would suggest. Sorry about that. Managed to get some quality time in the shop, and made some noise and some sparks...

Nut-serts, rivinuts, whatever you want to call them.

Bearings and cross-shaft.

Rough mock up of what will be the foot-pedal pump up mechanism. Simple enough, but has to cope with the fact that the ram moves through an arc as the thing lifts. And the fact that I'm bodging this up as I go along, so everything has to be adjustable and easily altered as I figure out what will work and what won't.

Lowering handle, also has enough play not to jam as the thing goes up and down. Can I say that, as an engineer, this is perhaps not my proudest moment. But what the heck, it works...

Pump pedal return spring. Actually a side stand spring picked up at an auto jumble ages ago. Knew it would come in useful one day.